The present invention relates to a nonaqueous electrolyte secondary battery having an improved negative electrode and a method of manufacturing a negative electrode.
Nonaqueous electrolyte secondary batteries represented by a lithium-ion secondary battery have a high energy density and are extensively used in portable apparatuses such as portable telephones, portable information terminals, and personal computers. To further decrease the sizes and weights of these apparatuses, batteries as their power supplies are required to have a higher energy density, and researches are being made to increase the capacity of the electrode material.
Of these researches, the use of carbonaceous materials such as activated carbon and graphite as a negative electrode material is examined in, e.g., Jpn. Pat. Appln. KOKAI Publication Nos. 58-35811 and 59-143280.
Unfortunately, secondary batteries including negative electrodes containing known carbonaceous materials have a small discharge capacity. Therefore, it is being demanded to develop a negative electrode material capable of further increasing the capacity.
It is an object of the present invention to provide a large-capacity nonaqueous electrolyte secondary battery.
It is another object of the present invention to provide a method of manufacturing a high-performance negative electrode.
The present invention provides a nonaqueous electrolyte secondary battery comprising a negative electrode containing a carbonaceous material aggregate having a structure in which carbonaceous material plates are three-dimensionally distributed, the carbonaceous material plates being capable of absorbing and desorbing lithium ions and having a molar ratio of hydrogen to carbon of 0.2 to 0.4.
The present invention also provides a method of manufacturing a negative electrode containing a carbonaceous material which is capable of absorbing and desorbing lithium ions, wherein the carbonaceous material is formed by a method comprising the step of heat-treating a carbonaceous material precursor containing at least one substance selected from the group consisting of a metal salt of an aromatic compound and a metal complex of an aromatic compound at 500 to 1500xc2x0 C. in an inert gas ambient.
Additional object and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The object and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.